Magnet cap

ABSTRACT

One or more method(s), system(s), and/or device(s) produces an assembly for securing a product to a dissimilar material, such as a magnet to plastic. A magnet assembly may include a plastic cap having one or more wings extending laterally from a side surface of the plastic cap. A plastic holder defines a product cavity and has one or more grooves formed to integrally fit with the one or more wings of the plastic cap. A magnet is positioned within the product cavity. The plastic cap is joined to the plastic holder, such as through staking or welding, to capture the magnet within the product cavity.

This application is a divisional of U.S. patent application Ser. No.12/203,437, filed Sep. 3, 2008, now U.S. Pat. No. 7,986,206 whichapplication claims the benefit of U.S. Provisional Application No.60/969,930, filed Sep. 4, 2007, the entire contents of which are hereinincorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This description generally relates to securing magnets within or toplastic parts, and more particularly to one or more methods, devices,and/or systems for attaching a magnet or other non-plastic part to aplastic part in a variety of manufacturing applications.

2. Description of the Related Art

The staking of plastic materials is one technique for joining materials,such as thermoplastic materials. There are four common methods ofstaking, including cold staking, heat staking, thermo staking, andultrasonic staking or welding. The choice of the joining process isoften dependent upon the materials to be joined, the loads to which theassembly will be subjected and/or the required cosmetic appearance.

In each case, accurate alignment of the components is important to thequality of the joint. The common design parameters may include studdiameter, stud height and stud geometry. Due to the deformation ofpreviously formed parts, effective staking is often restricted tothermoplastic materials. For example, in heat staking, a probe is heatedso that less pressure is required to form a head on a stud. This widensthe application of staking to a broader spectrum of thermoplasticmaterials than is possible with cold staking, including glass-filledmaterials. The quality of the joint is dependent on control of theprocessing parameters: temperature, pressure and time—a typical cycletime might be between 1 to 5 seconds.

Heat staking has the advantage that parts can be disassembled. It alsohas the flexibility to allow the simultaneous formation of a largenumber of studs and to accommodate a variety of stud head designs.

SUMMARY OF THE INVENTION

The present inventors have determined that the use of staking processesto join dissimilar materials, such as in the manufacture oftelecommunications devices may produce inconsistent results. Forexample, heat-staking a magnet directly to a plastic part within amass-produced telephony device may produce inconsistent results in highvolume manufacturing, e.g., inconsistency in location and dimensionaltolerances from telephony device to telephony device.

Alternatively or in addition, a magnet secured in a conventional housingor recess with heat staking may be easily broken loose from the plasticpart, e.g., even when the magnet is held in place properly thedifference between the coefficients of expansion of the magnet and theplastic results in the magnet not being held securely in place, suchthat the magnet may rattle within the telephone enclosure.

The present invention allows the use of several joining processes,including staking processes to securely, accurately, and consistentlyjoin a magnet or other material to a plastic part.

In one general aspect, a method for securing a product having adissimilar material to a plastic part includes positioning the productwithin a recess of a bucket having stepped grooves. A cap is positionedover the bucket, wherein one or more wings of the cap integrally fitwithin the grooves of the bucket. The cap is joined to the bucket toform an assembly. The product is encapsulated within the bucket and thecap by one or more ribs extending away from the cap or bucket.

Implementations of this aspect may include one or more of the followingfeatures. For example, the cap may be joined to the bucket by heatstaking the cap to the bucket. The cap may be joined to the bucket byultrasonic welding. The cap and bucket may comprise thermoplastic, suchas acrylonitrile butadiene styrene (ABS) thermoplastic. The product mayinclude a magnet, such as a cylindrically shaped magnet formed to fitwith an interference fit within the bucket.

In another general aspect, a magnet assembly includes a magnet caphaving one or more wings extending laterally from a side surface of themagnet cap, a magnet bucket defining a product cavity and having one ormore grooves formed to integrally fit with the one or more wings of themagnet cap, and a magnet positioned within the product cavity, whereinthe magnet cap is joined to the magnet bucket to encapsulate the magnetwithin the product cavity.

Implementations of this aspect may include one or more of the followingfeatures. For example, the magnet cap and/or magnet bucket may comprisethermoplastic, such as ABS thermoplastic. The magnet cap may comprisetwo, three, or more wings. The magnet bucket may comprise two or three,or more, stepped grooves shaped to integrally secure a portion of thetwo or three, or more, respective wings of the magnet cap therein. Themagnet cap may be joined to the magnet bucket through staking, such asheat staking or ultrasonic staking (welding). The magnet cap may includeone or more ribs extending from an underside of the magnet cap into theproduct cavity to securely engage the magnet therein. The magnet cap mayinclude one or more stepped edges on an upper side thereof, the steppededges being formed to integrally fit with one or more attachment ribs onthe magnet bucket which define the one or more grooves of the magnetbucket. The magnet cap may include a substantially round body portionand the one or more wings may extend generally laterally away from acenter of the round body portion. The magnet bucket may comprise asubstantially cylindrical body portion which defines the product cavity.The cylindrical body portion may further include the one or more ribs ofthe magnet bucket which define the one or more grooves of the magnetbucket. The magnet may be a substantially cylindrically shaped magnetwhich fits with an interference fit within the product cavity whenencapsulated by the joined magnet cap and magnet bucket.

Implementations of this aspect may include one or more of the followingfeatures. For example, the magnet cap may include multiple wings, e.g.,two, three, four-winged configurations, for securing to a bucket. Themagnet may be secured to the magnet cap or to the magnet bucket prior tojoining the magnet cap to the magnet bucket. The magnet cap may beremoved for access to the magnet held within the magnet bucket forinspection and/or replacement, e.g., if a heat staking joining processis utilized.

Further scope of applicability of the present invention will becomeapparent from the detailed description given hereinafter. However, itshould be understood that the detailed description and specificexamples, while indicating preferred embodiments of the invention, aregiven by way of illustration only, since various changes andmodifications within the spirit and scope of the invention will becomeapparent to those skilled in the art from this detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from thedetailed description given hereinbelow and the accompanying drawingswhich are given by way of illustration only, and thus, are not limits ofthe present invention, and wherein:

FIG. 1 is a perspective view of a top of a cap in accordance with thepresent invention;

FIG. 2 is a perspective view of a bottom of the cap of FIG. 1;

FIG. 3 is an exploded view of a bucket, a magnet and the cap of FIGS. 1and 2 illustrating an assembly method;

FIG. 4 is perspective view of a top of the assembled bucket, magnet andcap prior to an attaching step;

FIG. 5 is a perspective view of the top of the assembled bucket, magnetand cap after the attaching step;

FIG. 6 is a cross sectional view taken along line VI-VI in FIG. 4;

FIG. 7 is a perspective view of a top of a cap in accordance with asecond embodiment of the present invention;

FIG. 8 is a perspective view of a bottom of the cap of FIG. 7;

FIG. 9 is a perspective view of the cap of FIGS. 7 and 8 assembled on abucket adjacent to an obstruction;

DETAILED DESCRIPTION OF THE INVENTION

The present invention now is described more fully hereinafter withreference to the accompanying drawings, in which embodiments of theinvention are shown. This invention may, however, be embodied in manydifferent forms and should not be construed as limited to theembodiments set forth herein; rather, these embodiments are provided sothat this disclosure will be thorough and complete, and will fullyconvey the scope of the invention to those skilled in the art.

FIG. 1 is a perspective view of a top of a plastic cap 11, in accordancewith the present invention. In one embodiment, the plastic cap 11 isformed of a thermoplastic, such as acrylonitrile butadiene styrene (ABS)thermoplastic. The plastic cap 11 includes a substantially roundmidsection 13. One or more wings 15 extend laterally from a side surfaceof the plastic cap 11. In the illustration of FIG. 1, three wings 15-1,15-2 and 15-3 extend away from a center of the midsection 13. Steppededges 17 may optionally be provided between the wings 15. In theillustration of FIG. 1, three stepped edges 17-1, 17-2 and 17-3 existbetween the three wings 15-1, 15-2 and 15-3.

FIG. 2 is a perspective view of a bottom of the plastic cap 11 ofFIG. 1. FIG. 2 illustrates the presence of at least one ramp-shaped rib21 extending away from the plane of the midsection 13 in a directionsubstantially perpendicular to the lateral extension of the wings 15. Inthe illustration of FIG. 2, three ramp-shaped ribs 21-1, 21-2 and 21-3exist on the bottom of the plastic cap 11. Each rib 21 tapers from abase attached to the plastic cap 11 to a relatively narrower free end.

FIG. 3 is an exploded view illustrating an assembly of the plastic cap11 of FIGS. 1 and 2 and a non-plastic part 23 and a plastic holder 25,such as a plastic bucket. In one embodiment, the non-plastic part 23 isa disc-shaped magnet. Although a magnet has been illustrated, thenon-plastic part 23 could be formed of other materials dissimilar toplastic, such as metal, wood, glass or ceramic.

The plastic holder 25 forms a recess or product cavity 27. In oneembodiment, the product cavity 27 is cylindrical in shape, such that thenon-plastic part 23 can fit therein. Typically, the plastic holder 25 isattached to, or integrally formed with, a plastic base 35, which forms afloor for the product cavity 27. In one embodiment, the plastic holder25 is formed of a thermoplastic, such as acrylonitrile butadiene styrene(ABS) thermoplastic.

A rim defining an opening to the product cavity 27 includes at least onegroove 29 formed therein. In the illustration of FIG. 3, three grooves29-1, 29-2 and 29-3 exist along the rim of the product cavity 27. Thethree grooves 29-1, 29-2 and 29-3 are sized to accept, in a closefitting relationship, the three wings 15-1, 15-2 and 15-3 of the plasticcap 11. Attachment ribs 31 may optionally be provided on the plasticholder 25 on the upstanding portions 33 defining the grooves 29. In theillustration of FIG. 3, three rounded attachment ribs 31-1, 31-2 and31-3 face inwardly from three upstanding portions 33-1, 33-2 and 33-3along the periphery of the product cavity 27.

Now, with reference to FIGS. 3-6, a method for securing the non-plasticpart 23 to the plastic holder 25 will be described. First, thenon-plastic part 23 is positioned within the product cavity 27 of theplastic holder 25. Next, the plastic cap 11 is superimposed orpositioned over the plastic holder 25. The one or more wings 15 of theplastic cap 11 are fitted within the corresponding one or more grooves29 of the plastic holder 25.

As best seen in the cross sectional view of FIG. 6, as the plastic cap11 is pressed onto the plastic holder 25, the ramp-shaped ribs 21 engagea side surface of the non-plastic part 23 to wedge the non-plastic part23 within the product cavity 27 with an interference fit. If theoptional stepped edges 17-1, 17-2 and 17-3 are provided on the plasticcap 11 and the optional attachment ribs 31-1, 31-2 and 31-3 are providedon the plastic holder 25, these features may snap past each other tohold the plastic cap 11 on the plastic holder 25.

Finally, while the plastic cap 11 is fully seated onto the plasticholder 25, the plastic cap 11 and plastic holder 25 are joined by afixed joint to capture the non-plastic part 23 in the product cavity 27and form an assembly 37. The fixed joining of the plastic cap 11 and theplastic holder 25 can be accomplish by cold staking, heat staking,thermo staking, ultrasonic staking or welding, or any other known meansof joining two like plastic parts. FIG. 5 is a perspective view of theassembly 37 of the plastic cap 11 joined to the plastic holder 25 byheat staking. As seen in FIG. 5, the assembly 37 is substantiallyuniform in shape, as the individual elements of the plastic holder 25and the plastic cap 11 have become joined together and substantiallyindistinct from each other during the heat staking process.

FIGS. 7 and 8 illustrate a modified cap 41 in accordance with analternative embodiment of the present invention. FIG. 7 is a perspectiveview of a top of the modified cap 41. FIG. 8 is a perspective view of abottom of the modified cap 41 of FIG. 7. Like elements to the plasticcap 11 of FIGS. 1 and 2 have been labeled with the same referencenumerals.

A primary distinction between the modified cap 41 and the plastic cap 11of FIGS. 1 and 2 is that the third wing 15-3′ is greatly shortened sothat it substantially follows the outer circular periphery of themidsection 13 of the modified cap 41.

As best illustrated in FIG. 9, when the plastic holder 25 is located ona portion of the plastic base 35 which is immediately adjacent to anobstruction 51, like the protruding channel, the modified cap 41 can beemployed to avoid interference with the obstruction 51. As illustratedin FIG. 9, the short wing 15-3′ is placed in the groove 29-3 between theupstanding portions 33-2 and 33-3. By this arrangement, the modified cap41 will not contact the obstruction 51, whereas the plastic cap 11 ofFIG. 1 could not have been employed with the plastic holder 25 of FIG.9, because the third wing 15-3 would have interfered with theobstruction 51 and not fully seated onto the plastic holder 25.

Another distinction of the modified cap 41 is that the modified cap 41has only two ramp-shaped ribs 21-1 and 21-2. The primary purpose of theramp-shaped ribs 21 is to hold the non-plastic part 23 within theproduct cavity 27 with an interference fit so that the non-plastic part23 will not rattle within the product cavity 27. This may beaccomplished with two ramp-shaped ribs 21 (as illustrated in FIG. 8) oreven one ramp-shaped rib 21.

Although FIGS. 2, 6 and 8 illustrated the ramp-shaped ribs 21 as beingattached to the plastic cap 11/14 it would be possible to have theramp-shaped members 21 attached to the floor of the product cavity 27.Under either circumstance, the ramp-shaped ribs 21 would engage the sideedges of the non-plastic part 23 to hold the non-plastic part 23 in theproduct cavity 27 with an interference fit, which prevents thenon-plastic part 23 from rattling within the product cavity 27.

The caps 11 and 41 and holder 25 have been described as being formed ofacrylonitrile butadiene styrene (ABS) thermoplastic. ABS is a copolymerderived from acrylonitrile, butadiene, and styrene. The advantage of ABSis that this material combines the strength and rigidity of theacrylonitrile and styrene polymers with the toughness of thepolybutadiene rubber, producing a tough, impact and heat resistantproduct. In addition, ABS plastics have desirable electrical properties.However, it should be appreciated that other materials may be employedin the present invention to achieve one or more of these recognizedadvantages to differing degrees.

The caps 11 and 41 and holder 25 of the present invention providegreater dimensional consistency in high-volume manufacturing. They alsoprovide a much stronger attachment of a magnet or other non-plastic part23, thus extending the life-expectancy of the ultimate product. Oneapplication of the present invention is to use the plastic cap 11/41 andplastic holder 25 in a telephone set, such as an Avaya desktoptelephone, to attach a magnet within the telephone base.

The invention being thus described, it will be obvious that the same maybe varied in many ways. Such variations are not to be regarded as adeparture from the spirit and scope of the invention, and all suchmodifications as would be obvious to one skilled in the art are to beincluded within the scope of the following claims.

1. A magnet assembly comprising: a telephony device; a plastic holderhaving a recess, wherein said plastic holder is attached to saidtelephony device; a magnet disposed within said recess; a plastic capsuperimposed over said magnet; and a fixed joint formed between saidplastic holder and said plastic cap, such that said plastic cap and saidplastic holder become joined together and substantially indistinct fromeach other at said fixed joint, to capture said magnet within saidrecess of said plastic holder.
 2. The magnet assembly according to claim1, wherein said plastic cap and said plastic holder are formed of athermoplastic.
 3. The magnet assembly according to claim 2, wherein saidthermoplastic is acrylonitrile butadiene styrene (ABS) thermoplastic. 4.The magnet assembly according to claim 1, wherein said plastic cap isjoined to said plastic holder by heat staking or ultrasonic welding. 5.The magnet assembly of claim 1, wherein said recess is cylindrical inshape, and wherein said magnet is disc-shaped.
 6. The magnet assemblyaccording to claim 1, wherein said plastic cap or said plastic holderincludes at least one ramp-shaped rib engaging said magnet to wedge saidmagnet into an interference fit within said recess.
 7. The magnetassembly according to claim 6, wherein said at least one ramp-shaped ribengages a side surface of said magnet to wedge said magnet into aninterference fit within said recess.
 8. The magnet assembly of claim 1,wherein said plastic holder is attached to an enclosure of saidtelephony device.
 9. The magnet assembly of claim 8, wherein saidtelephony device is a desktop telephone.
 10. The magnet assemblyaccording to claim 1, wherein said plastic holder includes at least onegroove and said plastic cap includes at least one wing to fit withinsaid at least one groove of said plastic holder, and wherein said fixedjoint is formed between said at least one wing of said plastic cap andsaid at least one groove of said plastic holder.
 11. The magnet assemblyaccording to claim 10, wherein said at least one wing of said plasticcap includes three wings extending laterally from a side surface of saidplastic cap and said at least one groove of said plastic holder includesthree grooves formed to accept said three wings of said plastic cap. 12.The magnet assembly according to claim 11, wherein said plastic cap isjoined to said plastic holder by heat staking or ultrasonic welding saidthree wings of said plastic cap to said three grooves of said plasticholder.
 13. The magnet assembly according to claim 10, wherein saidplastic cap and said plastic holder are formed of a thermoplastic. 14.The magnet assembly according to claim 13, wherein said thermoplastic isacrylonitrile butadiene styrene (ABS) thermoplastic.
 15. The magnetassembly according to claim 10, wherein said plastic cap or said plasticholder includes at least one ramp-shaped rib engaging said magnet towedge said magnet into an interference fit within said recess.
 16. Themagnet assembly according to claim 15, wherein said at least oneramp-shaped rib engages a side surface of said magnet to wedge saidmagnet into an interference fit within said recess.
 17. A magnetassembly comprising: a plastic holder having a recess and at least onegroove; a magnet disposed within said recess; a plastic cap superimposedover said magnet, said plastic cap including at least one wing to fitwithin said at least one groove of said plastic holder; and a fixedjoint formed between said plastic holder and said plastic cap, whereinsaid fixed joint is formed between said at least one wing of saidplastic cap and said at least one groove of said plastic holder, tocapture said magnet within said recess of said plastic holder, whereinsaid plastic cap or said plastic holder includes at least oneramp-shaped rib engaging said magnet to wedge said magnet into aninterference fit within said recess.
 18. The magnet assembly of claim17, wherein said at least one ramp-shaped rib engages a side surface ofsaid magnet to wedge said magnet into an interference fit within saidrecess.
 19. The magnet assembly of claim 17, wherein said plastic holderis part of a telephony device.
 20. The magnet assembly of claim 19,wherein said telephony device is a desktop telephone.